First Time Conducting, No Experience - Need Help!

I am a junior in high school and recently I was put in charge of the music for my church's teen mass. I'm really excited because I love music and helping others, but my problem is that I have zero expierence. Honestly, I don't know what I'm doing. I play the violin in my school orchestra (have been playing since I was 4) and personally, I don't think that I'm a good singer. I can read music and understand what sounds good/what sounds bad. My main duties with this job include: running rehearsals, conducting the choir during mass, choosing music, and helping the instruments with their music. I'm super nervous and don't really know what to expect. I have my church's youth leader & adult choir conductor help if I need it....but if anyone has any tips/advice they could give me, that would be absolutley fantastic.